The invention is directed to an arrangement for changing the bobbin of a sewing or embroidery machine, and more particularly relates to a release and hold means for moving the bobbin out of the hook base and for conveying the bobbin into a changing position.
The maximum amount of thread that can be stored on a bobbin for a sewing or embroidery machine is extremely limited due to geometric conditions. The amount that can be stored covers only a fraction of the amount of thread that can be stored on the bobbin for the needle thread and therefore must be changed often. Another disadvantage of this small amount of thread is that changing the bobbin, which is usually held in a bobbin case mounted in the hook, is very involved. Access to the hook, which is located underneath the needle plate, is naturally poor and especially during stitching or quilting, access to the bobbin is made more difficult by the material to be sewn lying on the needle plate.
In the state of the art, the following various attempts have already tried to improve these conditions.
From DE-10 032 011, it is known to manufacture the bobbin at least partially from ferromagnetic material, so that it can be moved out of the hook by a magnetic discharge element. This known arrangement requires bobbins manufactured especially for this discharge arrangement and it cannot use conventional bobbins made from non-magnetic material, such as stainless steel and plastic, which are most readily available. For this known arrangement, not only the bobbin, but also the hook must be configured correspondingly in order to retain the ferromagnetic bobbin by magnetic attraction within its housing during sewing. The retention is realized not by a positive-fit, but instead only by a force-fit by means of magnetic force of attraction. Consequently, this known bobbin discharge arrangement requires not only special bobbins, but also a correspondingly formed hook.
From EP-A1-0829 565, a hook exchanger is further known, which is suitable for commercial sewing machines. A handling device removes the bobbins filled with thread and inserted into a bobbin case from a rotary star and inserts them into the hook of the machine. In the reverse sequence, the bobbin case containing an empty thread bobbin is removed from the machine beforehand and conveyed to the handling device. Such handling devices are on one hand expensive and only usable in commercial machines. In addition, they can by used only to a limited extent in free-arm household sewing machines, because the free arm no longer allows sewing of tubular goods due to the handling device.
From CH 369955, a bobbin removal arrangement is further known, which enables the removal of the bobbin by sliding a cover on the sewing table. This arrangement, like the first, requires a specially formed hook and a complicated mechanism arranged underneath the needle plate in the machine housing. If something goes wrong, the removal of the bobbin by hand is barely possible without the help of a technician.